There's been much debate about whether or not burning wood for heat really is green. But the debate over wood-based biomass energy is only likely to heat up (sorry!) now that coal power plants are beginning to burn wood pellets instead. While some tout lower carbon emissions, others claim that large-scale burning of trees for power is fundamentally unsustainable — and may even result in increased emissions once land use changes and transportation are taken into account.

There are, however, other forms of wood-based biomass power that are less controversial. For example, that a coalition of investors has committed to building the U.K.'s first wood gasification power plant, which will divert wood-based waste from a landfill and instead convert it to syngas, a cleaner burning fuel that will be used to drive turbines and generate electricity. Here are the details as reported at BusinessGreen:

The Birmingham Bio Power plant will convert recovered wood into electricity through a gasification process in which carbon in wood is converted into gas, which is then used to raise steam to drive a turbine. The 10.3MW project is being developed by Carbonarius — a joint venture between Stoke-on-Trent technology developer O-Gen and property firm The Una Group. It is aiming for completion in 2016, in time to secure payments from the Renewable Obligation Certificate subsidy regime.

Gasification is a relatively old technology. In fact, it's been around in one form or another since the 1700s. It's a process that can be fueled by any number of feedstocks including crop residues, coal or — in this case, waste wood. Instead of burning the feedstock, a gasification plant heats it up with very little oxygen at extremely high temperatures, setting off a series of chemical reactions that result in a gaseous mixture made up primarily of carbon monoxide and hydrogen. (According to How Stuff Works, carbon dioxide can even be removed during gasification and either stored underground or used for industrial purposes.) That cleaner-burning gas can then be used as a fuel for a number of different applications, in this case being burned to generate electricity.

According to investors, the plant will prevent 2.1 million tonnes of CO2 equivalent from being released and, over its 20-year lifetime, will save around 1.3 million tonnes of wood from landfill. There is, however, only so much waste wood available — and plenty of other potential uses for much of it, including reclaiming it for future construction. In the long run, the question of sustainable sources of feedstocks will be a central concern for any large-scale expansion of wood gasification.

Scot Quaranda is communications director for Dogwood Alliance, a group that has been a vocal critic of Europe's push to burn biomass instead of coal. (Disclosure: Dogwood Alliance is a client in my day job.) According to Quaranda, even plants burning purely waste wood should be watched very carefully:

"Strictly using wood that would otherwise be going to landfill is one thing, but you have to ask whether there are higher uses for that material. You also have to be concerned about potential "feedstock creep." As soon as you generate economic demand for a supposedly waste product, you create an incentive for the market to produce that product in greater quantities — and that can easily lead to an increase in industrial logging."

It's an interesting point. Once you find a use for a waste product, then it's no longer waste. And if you're paying for that product, then you are supporting the activities that produced it. A waste-to-power gasification plant may reduce landfill usage in the short-run, but how will it fit into a truly low-carbon economy where waste is no longer so easy to come by?